Catheters are well known in the medical field. The typical procedure for inserting a catheter into a patient is to first feed a guide wire into the patient until the distal end of the guide wire has reached a target location inside the patient, for example, a portion of a blood vessel that has a stenosis. Once the guide wire is in place, a catheter is feed through the proximal end of the guide wire. The catheter is then feed into the patient and tracked along the guide wire until the catheter has also reached the target location.
In a exemplary application, a percutaneous transluminal coronary angioplasty (PTCA) catheter is feed through a guide wire that has been inserted into a patient until the balloon carried by the PTCA catheter has reached the target location (e.g., location of stenosis). The balloon is then inflated in order to expand the vessel at the location of the stenosis. After the balloon has been inflated at the target location, it is deflated and the catheter is pulled back from the target area.
There are in general two main ways by which catheters track over a guide wire, the first is an "over-the-wire" design in which the guide wire lumen extends from the far distal tip of the catheter to the far proximal end. The second is a monorail system where the guide wire lumen is shorter than the catheter.
The advantage of the monorail (also call "rapid exchange") design is that the shorter guide wire lumen allows a single operator to change catheters conveniently. In one embodiment of the monorail system, the guide wire lumen is very short in length, for example, less than 2 centimeter (cm) and the guide wire lumen is positioned at the far distal tip of the catheter. In these catheters where you have a short distal exchange guide wire lumen, by construction the guide wire exit portion (the proximal end guide wire port) may be in the tortuous portion of the vessel causing the catheter to potentially snag the guide wire. The problem that some times occurs when such a catheter is being pushed or pulled back along the guide wire is that the catheter may grab the guide wire and drag it along, especially when the catheter is being moved along a tight bend in the vessel. This grabbing or snagging of the guide wire by the catheter affects the proper placement of the guide wire. The correction of this problem is for the physician to work the guide wire back to its proper location. This sometimes may take a long period of time to accomplish, especially if the guide wire has gone through several tight bends. Given that time is of the essence when a patient is undergoing a surgical procedure such as PCTA, a need exists in the art for a catheter, which can minimize the above-mentioned problem.